1-Lower alkyl-4,5-dihydro-5-phenyl-2-lower alkoxycarbonylaminoimidazoles, and substituted phenyl derivatives thereof, and pharmaceutically acceptable salts thereof, and methods of preparing such compounds. In one method, the compounds can be prepared by treating the corresponding .beta.-lower alkylamino-.beta.-(phenyl or substituted phenyl)-ethylamine with the desired 1,3-bis (alkoxycarbonyl)-S-methylisothiourea or 1-alkoxycarbonyl-S-methylisothiourea. The compounds can also be prepared by treating the corresponding 1-lower alkyl-2-amino-4,5-dihydro-5-(phenyl or substituted phenyl)-imidazole with the desired dialkylcarbonate. The subject compounds are useful as psychotherapeutic agents in treating or palliating abnormal conditions, in mammals, which involve the central nervous system.